fission

1 of 2

noun

fis·​sion ˈfi-shᵊn How to pronounce fission (audio)
-zhᵊn
1
: a splitting or breaking up into parts
2
: reproduction by spontaneous division of the body into two or more parts each of which grows into a complete organism
3
: the splitting of an atomic nucleus resulting in the release of large amounts of energy
fissional adjective

fission

2 of 2

verb

fissioned; fissioning; fissions

intransitive verb

: to undergo fission

transitive verb

: to cause to undergo fission

Example Sentences

Recent Examples on the Web
Noun
But if one persistent cadre of nuclear optimists are right, then Linglong One could be a model for fission’s future in an age of clean energy. IEEE Spectrum, 15 Jan. 2023 All existing nuclear plants use fission — splitting atoms apart — rather than fusion, which involves fusing them together. David R Baker, Bloomberg.com, 13 Dec. 2022 Fusion generates four times more energy per kilogram than the fission used to power nuclear plants and nearly four million times more energy than burning oil or coal, according to the International Atomic Energy Agency. Elizabeth Weise, USA TODAY, 13 Dec. 2022 Fusion differs from fission, the technique currently used in nuclear power plants, by fusing two atomic nuclei instead of splitting one. CBS News, 12 Dec. 2022 Unlike conventional nuclear fission, which produces highly radioactive waste and carries the risk of nuclear proliferation, nuclear fusion has no emissions or risk of cataclysmic disaster. Frank Holmes, Forbes, 27 Dec. 2022 While both process deal with changing the nucleus of atoms, fusion — the joining of atoms — is a different process than fission, which involves splitting atoms. USA Today, 16 Dec. 2022 Unlike nuclear fission, the process that powers today’s nuclear power plants, fusion energy poses no risk of out-of-control chain reactions and meltdowns, like the disaster in Chernobyl in 1986. Avery Hurt, Discover Magazine, 13 Dec. 2022 Nuclear energy releases millions of times as much energy as other forms and fusion is much more powerful than fission – that’s why hydrogen bombs are more destructive than atomic ones. Don Lincoln, CNN, 14 Dec. 2022
Verb
Most atoms do not fission, but the isotopes of certain elements, such as uranium-235, are fissile. Washington Post, 28 Apr. 2022 The point is that by analyzing the array of radioactive fission products – those that can be captured and analyzed – nuclear forensic specialists can start to figure out if the atoms that fissioned were U-235, Pu-239, or (in some cases) U-238. Andrew Karam, Popular Mechanics, 7 Jan. 2016 Anyone can see that fissioning uranium 235 or plutonium can be used to generate electricity. Scientific American, 1 Jan. 2018 See More

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'fission.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

Word History

Etymology

Noun

borrowed from Latin fissiōn-, fissiō, from fid-, variant stem of findere "to split, cleave" + -tiōn-, -tiō, suffix of verbal action — more at bite entry 1

Verb

derivative of fission entry 1

First Known Use

Noun

circa 1617, in the meaning defined at sense 1

Verb

1929, in the meaning defined at intransitive sense

Time Traveler
The first known use of fission was circa 1617

Dictionary Entries Near fission

Cite this Entry

“Fission.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/fission. Accessed 27 Mar. 2023.

Kids Definition

fission

1 of 2 noun
fis·​sion ˈfish-ən How to pronounce fission (audio)
 also  ˈfizh-
1
: a splitting or breaking up into parts
2
: a method of reproduction in which a living cell or body divides into two or more parts each of which grows into a whole new individual
3
: the splitting of an atomic nucleus resulting in the release of large amounts of energy

fission

2 of 2 verb
fissioned; fissioning
ˈfish-(ə-)niŋ,
ˈfizh-
: to go through or cause to go through fission

Medical Definition

fission

noun
1
: a method of reproduction in which a living cell or body divides into two or more parts each of which grows into a whole new individual
2
b
: the splitting of an atomic nucleus resulting in the release of large amounts of energy

called also nuclear fission

fission verb
fissioned; fissioning ˈfish-(ə-)niŋ also ˈfizh- How to pronounce fission (audio)
fissional adjective

More from Merriam-Webster on fission

Last Updated: - Updated example sentences
Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!


Which Came First?

  • baby chick with a brown egg
  • hot take or cold shoulder?
Spell It

Hear a word and type it out. How many can you get right?

TAKE THE QUIZ
Solve today's spelling word game by finding as many words as you can with using just 7 letters. Longer words score more points.

Can you make 12 words with 7 letters?

PLAY